MOST UNDERRATED AIRCRAFT OF WWII?

[DarrenW]

Serious losses were inflicted on Japanese airpower, not by fighters, but by bombers.

You'll find no argument from me there. But let's not forget that without control of the air, which is often times provided by fighters, the bomber becomes extremely vulnerable and loses a lot of it's effectiveness to inflict serious losses on said enemy.

 

[pbehn]

It may well have had greater greater volumetric efficiency in general or especially over certain examples. However poppet valve engines have considerable variation in volumetric efficiency so unless we know what is being compared such a statement doesn't mean much.
That is to say that perhaps a sleeve valve cylinder shows a 2% increase over poppet cylinder A and a 10% improvement over poppet cylinder B.
Obviously the advantage over Cylinder B is substantial and even the difference between the sleeve valve and the average of the poppet valves is a noticeable one. However if the difference gets down to 2-3 % while the statement is still accurate does the cost/complication of the sleeve valve justify the development of engines using it?

There are many theories about engines that have fundamental theoretical superiority over others, whatever the theoretical strengths of sleeve valves are or were, getting them to work reliably was another thing.

 

[Shortround6]

They got them to work, what has never been answered is if the cost was worth it. Post war commercial Hercules and Centaurus engines were powerful, economical in fuel and had very hi times between overhauls. But if we don't know the cost of the engines or the cost to overhaul them, then we have no real basis for figuring out if they were better than the poppet engines which were posting overhaul times of well over 1000 hours.
Since we also have no ideas of the R&D costs leading up to WW II (or the first few years of WW II) we don't know if the they made enough engines to really justify the costs.

 

[pbehn]

They got them to work, what has never been answered is if the cost was worth it. Post war commercial Hercules and Centaurus engines were powerful, economical in fuel and had very hi times between overhauls. But if we don't know the cost of the engines or the cost to overhaul them, then we have no real basis for figuring out if they were better than the poppet engines which were posting overhaul times of well over 1000 hours.
Since we also have no ideas of the R&D costs leading up to WW II (or the first few years of WW II) we don't know if the they made enough engines to really justify the costs.

I use the Typhoon as a guide, I don't know if they actually flew them back to the UK to scrap them, when the war ended. In poppet valve engines minor differences of machining can "bed in" on a sleeve valve engine everything is moving in circles and orbits rubbing things away. As you allude to, the pistons wear the sleeves and the sleeves wear the block or guides, it isn't an overhaul it is basically a new engine.

 

[Shortround6]

I use the Typhoon as a guide, I don't know if they actually flew them back to the UK to scrap them, when the war ended. In poppet valve engines minor differences of machining can "bed in" on a sleeve valve engine everything is moving in circles and orbits rubbing things away. As you allude to, the pistons wear the sleeves and the sleeves wear the block or guides, it isn't an overhaul it is basically a new engine.

Trying to give the Sleeve valve the benefit of the doubt and there were a lot more Bristol radials built than Sabres.

 

[pbehn]

Trying to give the Sleeve valve the benefit of the doubt and there were a lot more Bristol radials built than Sabres.

In theory I can see the benefits, and with todays machining technology and metallurgy I could see it working, but poppet valve engines have moved on too.

 

[wuzak]

It may well have had greater greater volumetric efficiency in general or especially over certain examples. However poppet valve engines have considerable variation in volumetric efficiency so unless we know what is being compared such a statement doesn't mean much.
That is to say that perhaps a sleeve valve cylinder shows a 2% increase over poppet cylinder A and a 10% improvement over poppet cylinder B.
Obviously the advantage over Cylinder B is substantial and even the difference between the sleeve valve and the average of the poppet valves is a noticeable one. However if the difference gets down to 2-3 % while the statement is still accurate does the cost/complication of the sleeve valve justify the development of engines using it?

A message I received from a former member....

This one notes the steady increase in Bristol Hercules TBO, right up to
3,500 hrs in Bristol Freighters working hard ferrying cars across Cook Strait
in NZ.

https://www.newcomen.com/wp-content/upl ... assell.pdf

& here below, Kevin Cameron describes some of the poppet valve problems encountered
by Wright R-3350 engines in hard-flown B-29's..

https://www.cycleworld.com/writing-abou ... y-davidson

 

[swampyankee]

The Spitfire, at least early in the war, has been reported to have had a significantly lower availability rate than the Hurricane.

 

[swampyankee]

Napier couldn't get sleeve valves to work without external help. Given the engines Napier put in service just before the Sabre, it's surprising the Air Ministry contracted with them for anything.

 

[J.A.W.]

Napier engines had accrued a number of merits...

Napier engines powered the World Land-speed record holder in 1939,
& Sabre* power was selected for an attempt on the World Air-speed title too.

Nothwithstanding problematic mass-production issues, the Sabre was the sole 'hyper' type
to see useful wartime service, & was the most powerful aero-engine ever, to pass service
type tests in the early 1940's..



*That specially 'fettled' Sabre then went into a regular service Typhoon, but I'd reckon
the squadron C.O. would've scored that one, for his 'personal' use..

 

[J.A.W.]

A message I received from a former member....

Links Fixed.

https://www.newcomen.com/wp-content/uploads/2012/12/Chapter-6-Hassell.pdf

Writing About Harley-Davidson

 

[J.A.W.]

They got them to work, what has never been answered is if the cost was worth it. Post war commercial Hercules and Centaurus engines were powerful, economical in fuel and had very hi times between overhauls. But if we don't know the cost of the engines or the cost to overhaul them, then we have no real basis for figuring out if they were better than the poppet engines which were posting overhaul times of well over 1000 hours.
Since we also have no ideas of the R&D costs leading up to WW II (or the first few years of WW II) we don't know if the they made enough engines to really justify the costs.

Simple 'cost' is often overridden by politico-economics..

The current supposed F1 cost-limitation by strict specification/longevity reg's is a case in point, it does not pan out..
( & akin to Grand Prix jockeys, fighter jocks don't care 'bout cost, they just want the juice, on tap!)

Sabres remained in RAF service, & were flown hard - through to the mid `50's - maybe to keep the Napier works going?

 

[J.A.W.]

Atlantic crossing at record speed.. & yet another interesting, innovative use for pre-WW 2 Napier aero-engines.

http://www.flightglobal.com/pdfarchive/view/1938/1938 - 2137.html

[flash]
]View: https://www.youtube.com/watch?v=bYtazEBQ1K8[/flash]

 

[J.A.W.]

& Member Bill Pearce - has featured this pre-WW2 Napier-powered fighter prototype in his excellent blogsite..

Martin-Baker MB2 Fighter

 

[Juha2]

I wouldn't put any Napier powered MB fighter to advertise Napier engine, firstly Baker was killed in Napier Sabre powered MB 3 proto when its Sabre failed during a take-off. Martin & Baker had asked for a RR Griffon but had to be content with a Sabre. Secondly Dagger wasn't a good engine, look the service history of Handley Page Hereford, Dagger powered version of Hampden. Napier had made good engines earlier, like Lion, but in 30s it had not a good track record.

 

[J.A.W.]

I wouldn't put any Napier powered MB fighter to advertise Napier engine, firstly Baker was killed in Napier Sabre powered MB 3 proto when its Sabre failed during a take-off. Martin & Baker had asked for a RR Griffon but had to be content with a Sabre. Secondly Dagger wasn't a good engine, look the service history of Handley Page Hereford, Dagger powered version of Hampden. Napier had made good engines earlier, like Lion, but in 30s it had not a good track record.

Juha, do you have a 'root cause analysis' which sheets home fault to the Sabre engine,
- in the case of Capt Bakers' fatal crash?

To judge by the Hawker Fury prototypes, which flew with all three current 'big' British mills, Centaurus/Griffon/Sabre,
the MB 5 would've performed even better, if Sabre powered.

I'd have to dispute your "...in 30s it had not a good track record" too..
- since John Cobb took the Brooklands outright lap record in his Napier-Railton at over 150mph..

As for the dismal H-P Hereford - as I recall, the engine development writer LJK Setright likened
the use of the Dagger, ( which was intended for a fighter, such as the MB 2) in a medium bomber,
as akin to putting a Formula 1 racecar engine in a bus, & then expecting it - to do well at the task..

 

[swampyankee]

Napier engines had accrued a number of merits...

View attachment 489408

Napier engines powered the World Land-speed record holder in 1939,
& Sabre* power was selected for an attempt on the World Air-speed title too.

Nothwithstanding problematic mass-production issues, the Sabre was the sole 'hyper' type
to see useful wartime service, & was the most powerful aero-engine ever, to pass service
type tests in the early 1940's..



*That specially 'fettled' Sabre then went into a regular service Typhoon, but I'd reckon
the squadron C.O. would've scored that one, for his 'personal' use..

Napier was also getting a reputation for poor quality control. One should also note that the Dagger was not used except on the Hereford and the Rapier only on the Seafox.

The success of the Napier Lion was, by this time, quite irrelevant: it was as obsolete as the Curtiss D-12 or the Liberty.

 

[J.A.W.]

Careful not to conflate the poor workforce cadre of the Liverpool 'shadow factory', & pitiful Napier management
with the skilled engineering talents at the original Napier Acton 'works'..

If you check the link featuring the Rapier-powered record-breaking Mercury sea-plane,
you'll see it was skippered by Capt Bennett, the Aussie pilot who went on to fame as
the Bomber Command Pathfinders boss..

&,

The venerable Lion was by no means irrelevant..

I'd bet you 'quids on' - that the suffering British tankcrews, 'up the blue' - in 'bloody Egypt' would've killed
to swap their ghastly 'Nuffield-Liberty' mills for a Sea Lion - which were earmarked for the RAF's own
high-speed sea rescue launches, & which reliably saved many a 'downed in the drink' aircrew..

 

[Shortround6]

The thing is that the Napier of 1938-42 was not the Napier of 1920-28.
Certainly not the only company to either rest on it's laurels or or take a wild tangent with change of management/designer/s.

Many English companies depended too much on just a few key personnel.
When A. J. Rowledge left in 1928 to go to Rolls-Royce there was nobody in house to take over. When Napair signed up Halford on a 'consultant' basis they pretty much sealed their fate. Initial agreement only covered air cooled engines of between 404.09 cu in and 718.39 cu in. Lion production was dropping like a rock and this was before the Depression of 1929. There was no new Napair engine to compete against the Kestrel or the Jaguar or the revamped Jupiter (Mercury & Pegasus).
The Rapier, while an interesting technical exercise, was never going to be a commercial success and I suspect the Air Ministry orders were as much to keep Napier in the game as they were actual get 'good' engines. Not that the Rapier was unreliable. It is just that 16 cylinders and 700lbs was not a cheap or light way to get 300hp. The Dagger was more of the same. 24 cylinders and 1300lbs was not commercially viable for 700-800hp in 1934-5. The Later Dagger VIII was too little, too late and had cooling problems as first used.

Any of the old 1920s aircraft engines were irrelevant to aircraft use in the late 30s and early part of the war.

The Lion was a fine engine in it's time but that time had come and gone. Use as a tank engine is debatable, it may very well have been a better engine than the Liberty (not that hard to do) but it might not have fit into the engine bay of some British tanks. The Lion was 42 in wide, the Liberty 27in. You not only have to stuff the engine into the bay, you have to perform maintenance on it while it is there so you need clearance for hands and arms. Maybe you can shift the fuel tanks on the side/s of the engine compartment to front as the LIon is shorter?

 

[wuzak]

Juha, do you have a 'root cause analysis' which sheets home fault to the Sabre engine,
- in the case of Capt Bakers' fatal crash?

The Sabre seized shortly after take-off due to the failure of a sleeve drive crank. He was at 100ft, and tried to make a landing, but had to avoid a farmhouse and, in doing so, his wing hit the ground.